Effect of Long Term Manuring on Soil Carbon Stock and Some Biological Properties under Rice – Rice Cropping System in an Inceptisol of Bhubaneswar, Odisha, India

This research was carried out to determine the effect of different manurial treatments on the quantity of carbon added to soil through stubble in rice-rice cropping system, organic carbon stock and its relation to biological properties in an Inceptisol of Bhubaneswar, Odisha. This has been contemplated in existing Long Term Fertilizer Experiment which is in progress since 1994 located in Central Research Station, OUAT with Rice-Rice cropping sequence. The experiment dealt with six treatments during the eighth crop cycle viz, 100% NPK, 100% NPK + FYM, 100% N, 100% NP, 100% NPK +Lime, control (no manuring) with 4 replications in a randomized block design. Both in the kharif and the rabi seasons, rice stubble with undisturbed roots was meticulously collected, processed, and tested for total carbon after rice harvest. The usual approach was followed when collecting and analyzing soil samples. Between 1223.5 and 2571.5 kg/ha of carbon and 2998.9 to 6330.85 kg/ha of total stubble were absorbed into the soil. After kharif and rabi, the surface carbon stock of the soil ranged from 7.41 to 12.50 Mg/ha and 7.14 to 11.76 Mg/ha, respectively. After kharif, the SOC of surface soil ranged between 3.48 and 6.51 g/kg and 3.35 and 6.13 g/kg. In 100% NPK+ FYM, the highest amounts of stubble, stubble carbon, and MBC were found. No manuring enhanced the BD (1.42 Mg/m3) but the addition of FYM and stubble decreased the BD (1.28 Mg/m3). MBC varied from 45.89 to 132.41 g of carbon per g of soil. The importance of subble addition in enhancing SOC was demonstrated by the significantly positive association between SOC and quantity of stubble addition (r = 0.85), carbon addition by stubble (r = 0.94), and carbon stock (r =0.91**). Similar to this, the MBC-SOC connection (r = 0.83**), which supported the contribution of SOC to collective formation. The strong positive link between SOC and MBC suggests that adding carbon helps to improve soil health, and rice straw is an excellent source of carbon. It needs to be suppressed in the soil.